High-nitrate wastewaters are known pose substantial risks to human and environmental health, while their effective treatment remains difficult. The denitrification of saline, high-NO3- wastewaters was investigated at the laboratory- and pilot-scale experiment. Complete denitrification was achieved for three different realistic wastewaters, and the maximum influent [NO3-]0 and salinity were as high as 20,500 mg/L and 7.8%, respectively. The results of microbial community structure analyses revealed that the sequences of denitrifying functional bacteria accounted for 96.2% of all sequences, and the functional genes for denitrification in bacteria were enriched with elevated salinity and [NO3-]0. A significant difference was observed in the dominant bacterial genus between synthetic and realistic wastewaters. Thauera and Halomonas species evolved to be the most common dominant genera contributing to the processes of nitrate, nitrite, and nitrous oxide reductase. This study is practically valuable for the treatment of realistic, saline, high-NO3- wastewaters via denitrification by heterotrophic bacteria.
Keywords: Denitrification; Expanded granular sludge bed reactor; High-NO(3)(−) wastewater; High-throughput sequencing; Microbial community structure.
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